The present invention relates to a circular type tension applying apparatus for uniformly applying tension to slit band plates. More particularly, the invention relates to a circular type tension applying apparatus for correcting an uneven tension in the slit band plates, after a process of slitting a wide, metal band plate into a number of band plates in a slitter line, the uneven tension which is caused in the wind-up process.
Generally, a wide band plate, when viewed in cross section, is not perfectly flat in shape. It is thick in the middle and thin at both ends. When the wide band plate is slit into band plates, slit band plates that were located in the middle are different in thickness from those that were located at both ends. When the slit band plates are wound up on a mandrel, the thick slit band plates wound around the mandrel are larger in diameter the thin slit band plates, a speed of winding up the slit band plates in the middle of the mandrel is different from the wind-up speed at both ends, and the slit band plates to be wound up are tensed nonuniformly. The slit band plates are more loosely wound up on the end parts of the mandrel than those wound up on the mid parts. Those slit band plates, when wound off the mandrel, are deformed telescopically or elliptically. The deformation of the slit band plates makes impossible the unwinding, transportation or the like of the slit band plates.
To prevent the slit band plates from being loosely wound up on the mandrel, the convectional art employs a by-roller tension applying apparatus or a tension pad apparatus, which applies tension to the slit band plates. However, those tension applying apparatuses also suffer from other problems. In the former, the slit band plates are nonuniformly tensed by the thickness difference, and in the latter, the surfaces of the slit band plates are scarred.
In U.S. Pat. No. 3,735,937, a tension applying apparatus which makes no scar on the surfaces of the slit band plates and can correct the unevenness of the wind-up tension caused by the thickness difference of the slit band plates is disclosed. This tension applying apparatus of U.S. Pat. No. 3,735,937, which uses endless belts, is constructed such that upper and lower groups of endless belts stretched between a pair of pulleys are oppositely disposed, each group of the endless belts being arrayed side by side in the transverse direction. Slit band plates is moved through a nip between the outer surfaces of the upper and lower groups of the endless belts. Pressure applying members disposed within the endless belts to vertically push the inner surfaces of the endless belts to press the endless belts against both sides of the slit band plates, the endless belts are cyclicaly turned together with the moving slit band plates. Tension is generated in the slit band plates by a frictional force generated through a slip, which takes place in the relative motion of the inner surfaces of the endless belts to the pressure applying members. And a coefficient of friction of the outer surfaces of the endless belts is higher than that of the inner surfaces la thereof. With such a construction, the slit band plates can be wound up free from a slip of the endless belts, and without scarring the slit band plates.
In the tension applying apparatus described above, the endless belts stretched between a pair of pulleys are circularly turned tracing a path of an elliptical shape, that is, repeatedly turned tracing linear paths between the pulleys and semicircular paths around the pulleys. Accordingly, the endless belts alternately experience a linear deformation when those travel along the linear path between the pulleys and a semicircle deformation when those travel along the semicircle path around the pulley. A bending resistance of the circularly turning endless belts is large. Particularly in the case of thin plates of low tension, the pressure of the belts against the band plates is small, so that a frictional force acting on the belts and the band plates is smaller than the bending resistance of the belts. This hinders a smooth circulation of the endless belts between the pulleys, and results in making a scar on the surfaces of the band plates. At this time, the surfaces of the endless belts are also scarred. Accordingly, the endless belts must be replaced by new ones frequently.
Since the linear deformation and the semicircular deformation are alternately repeated in the cyclicaliy turning endless belts, the material for the endless belts must be flexible, that is, easily worn. Accordingly, the endless belts made of such material must be replaced with new ones at relatively short intervals. The work of replacing a number of endless belts is troublesome and time consuming. During the replacing work, the wind-up work of the slit band plates is prohibited, resulting in poor efficiency of the wind-up work.
The present invention has been made in view of the above circumstances and has a first object to provide a circular type tension applying apparatus for slit band plates, the apparatus in which the endless belts are circularly turned tracing a path substantially of a circle, and no bending resistance is created in the circularly turning endless belts, thereby ensuring a smooth circulation of the endless belts, making no scar on the surfaces of the slit band plates, allowing use of the endless belts made of relatively hard material of less wear, and elongating the lifetime of the endless belts. A second object of the present invention is to a circular type tension applying apparatus for metal band plates, the apparatus which uses the endless belts having sufficient compressibility and restoration force in the thickness direction, thereby generating an additional tension in the slit band plates by a resistance force, which ensues from a deformation by compressive strain when those are sufficiently compressed in the thickness direction.